New membrane will help to ensure many parts of the world have easy access to drinking water.

One of the biggest, but least
appreciated problems facing many regions of the world is lack of clean drinking
water, a common problem in impoverished nations. Ironically, many of
these nations rest beside large bodies of salt water. Ttypically,
processing salt water into fresh water is expensive and requires large
dedicated plants.

DailyTech previously chronicled how wind-power driven desalinization plants which
used membranes were being developed. Now another major breakthrough in
the field has been devised, this time concerning the membranes.

Researchers from several international universities have developed a chlorine-tolerant membrane which
turns salt water into clean drinking water. Typically, salt water is
treated with chlorine to remove bacteria and microorganisms that would grow and
form a biofilm on the membrane, blocking it. However, chlorine destroys
past membranes which were build using amide-polymers (nitrogen based).
This meant that that the water had to be dechlorinated before being sent to the
membrane, a relatively expensive and complex process.

The new membrane is formed from sulfonated copolymers. It took
researchers Professor Benny Freeman with the The University of Texas at Austin,
James E. McGrath of Virginia Tech University, and Ho Bum Park of the University
of Ulsan in South Korea three years to develop the membrane for which they have
filed a patent. The new membrane is resistant to chlorine allowing the
elimination of dechlorination.

Says Professor Freeman, "If we make the desalination process more
efficient with better membranes, it will be less expensive to desalinate a
gallon of water, which will expand the availability of clean water around the
world. It promises to eliminate de-chlorination steps that are required
currently to protect membranes from attack by chlorine in water. We
believe that even a small increase in efficiency should result in large cost
savings."

Researchers also believe the design will help reduce carbon dioxide emissions
in developing nations by decreasing the electrical needs of the generation
process.

Professor Freeman explains:

Energy and water are inherently
connected. You need water to generate power (cooling water for electric
power generation stations) and generation of pure water requires energy to
separate the salt from the water. That energy is often generated from the
burning of fossil fuels, which leads inevitably to the generation of carbon
dioxide. Therefore, if one can make desalination more energy-efficient by
developing better membranes, such as those that we are working on, one could
reduce the carbon footprint required to produce pure water.

It was a
combination of luck and hard work that brought the researchers upon the novel
suflonated class of membranes. This class of materials enjoys a high
tolerance to aqueous chlorine, making it surprisingly a far better fit than
membrane materials currently in use.

Professor Freeman, who holds the Kenneth A. Kobe Professorship in Chemical
Engineering and the Paul D. & Betty Robertson Meek & American Petrofina
Foundation Centennial Professorship in Chemical Engineering, states,
"Basically, Dr. McGrath radically changed the chemical composition of the
membranes, relative to what is used commercially, and the new membranes do not
have chemical linkages in them that are sensitive to attack by chlorine."

The research was funded by the Office of Naval Research and the National
Science Foundation-Partnerships for Innovation Program.

The findings will be reported in a paper in this month's edition of the German
Chemical Society's journal, Angewandte Chemie, with Mehmet Sankir and
Zhong-Bio Zhang, both of Virginia Tech, as additional coauthors.

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